It is known that petroleum products, i.e., gas and liquid hydrocarbon products, contain or have associated with them corrosive materials such as carbon dioxide, hydrogen sulfide, and chlorides, etc. Aqueous fluids, such as those used in drilling and completion, can contribute salts, amines, acids, or other contaminants, causing the fluids to be corrosive. Crudes with high organic acid content such as those containing naphthenic acids are corrosive to the equipment used to extract, transport, and process the oil. Gases, such as hydrogen chloride, carbon dioxide and hydrogen sulfide generate highly acidic environments in the presence of aqueous conditions to which metallic surfaces become exposed. Further, naturally occurring and synthetic gases are often conditioned by treatment with absorbing acidic gases, e.g., carbon dioxide and hydrogen sulfide. Degradation of the absorbent and acidic components, as well as the generation of by-products, results in corrosion of metallic surfaces.
Besides the corrosion issue, there is a risk of leakage and associated fire protection and fire resistant issues in the handling of petroleum products. A loss of containment in any portion of the piping system may result in a high temperature, high heat flux, high velocity flame, frequently termed a “jet fire.” When there is a jet fire, extreme heat flux densities may occur together with high temperatures, depending on the nature of the fire. In the case of a fire involving the combustion of solid fuels (unlikely in most hydrocarbon processing operations), the temperature of the fire increases continuously and can be at 900° C. after 60 minutes, about 1050° C. after 120 minutes, and up to 1150° C. after 240 minutes. The heat flux density can reach up to 100 kW/m2. By comparison in hydrocarbon pool fires, the temperature rise can be more rapid and a temperature of 1150° C. can be reached after 20 minutes and with a heat flux density of 225 kW/m2. With a jet fire when natural gas and different condensates burn under high pressure, temperature can rise to 1300-1400° C. in a matter of seconds, with a heat flux density going up to 500 kW/m2.
Various approaches to controlling corrosion have been employed in the oil and gas industry including periodic monitoring and planned replacement of equipment, corrosion inhibitors, and equipment material upgrades. Operators select the appropriate approach, or combination of approaches, depending upon the nature, complexity, and predictability of the corrosion, the likelihood and consequences of equipment failure, and the ability to monitor and inhibit the corrosion. Each approach has risks and drawbacks. It is often not possible to monitor and plan an economic replacement schedule for equipment with a high degree of certainty. The use of inhibitors can have unintended side effects, such as moving the corrosion to other parts of the process or possibly posing some environmental concerns. When the cause of the corrosion is not known with certainty, or the causes of corrosion are numerous, or the corrosion varies with process changes, the selection of a resistant material is difficult and almost always very expensive.
Expensive steels and alloys, e.g., stainless steel, nickel-based high alloys, etc. materials, have been used in the oil & gas industry. Thermal cycling or thermal excursion has been known to affect structural components comprising metals in high-temperature oil & gas applications. Corrosion resistant fluoropolymer plastics such as Teflon™ can be used as liners in metal piping system. However, lined metal pipe systems can fail due to the differences in the physical properties of the liner and the metal pipe (e.g., viscoelastic properties due to thermal cycling). Teflon™ fluoropolymer plastic has a coefficient of thermal expansion that is ten times greater than carbon steel over a wide temperature range, but it is 75 times greater at 70° F. Teflon™ fluoropolymer plastic has an elastic modulus ranging from 58 to 80 MPa as compared to carbon steel with an elastic modulus of 190,000 MPa-210,000 MPa.
Because composite non-metallic materials provide improved corrosion resistance and reduced maintenance requirements, they have been employed as replacement of expensive steels and alloys. However, when structural components comprising nonmetallic composite materials are heated to their ignition or combustion support temperatures by heat transfer from a near-by flame, the materials ignite and/or support combustion, lose structural integrity, and evolve large quantities of smoke while burning. Further, the non-metallic materials must resist not only the temperatures and pressures encountered in oil and gas applications, but they almost must withstand the solvent, embrittling and other potential degrading properties of the hydrocarbons and contaminants contained in the process streams.
There is a continuing need for improved structural components with corrosion resistance and fire resistant properties for use in the handling of petroleum products. The invention relates to a structural component, e.g., a piping system, having the combined properties of composites, corrosion resistant materials, and thermal protective coatings for use in oil and gas applications.